Many industries often encounter particulate matter suspended in the atmosphere. In some industries, this particulate matter is a valuable product, for example, starch; it would be beneficial if these suspended particulate could be recovered and reintroduced into the process. For other industries, such as metal or wood working, the particulate matter may be simply dust; it is desirable to remove dust particles from the air in order to provide a clear working environment.
Systems for cleaning an air or other gas stream laden with particulate matter include air filter assemblies that have filter elements disposed in a housing. The filter element may be a bag or sock of a suitable fabric or pleated paper. The gas stream, contaminated with particulate, typically is passed through the housing so that the particulate are captured and retained by the filter element. Cleaning is accomplished by periodically pulsing a brief jet of pressurized air into the interior of the filter element to reverse the air flow through the filter element, causing the collected contaminants to be collected. Such air filter assemblies are disclosed in, for example, U.S. Pat. No. 4,218,227 (Frey) and U.S. Pat. No. 4,395,269 (Schuler), which patents are hereby incorporated by reference.
Cylindrical filter elements are usually used in an air filter assembly to process dust particles from an airstream. In a standard design of air filter assembly, an air filter assembly has a clean air chamber and a dirty air chamber. The two chambers are separated by a sheet metal, commonly referred to as a tube sheet. The tube sheet has a number of openings from which cylindrical filters are aligned. The filters suspend downwardly with or without an angle from the tube sheet openings into the dirty air chamber. Particulate-laden air is introduced into the dirty air chamber, and the particulates collect onto the filter. The filtered air passes through the filters to the interior of the filters, and upwardly out through the openings in the tube sheet into the clean air chamber. From the clean air chamber, the cleaned air is exhausted into the environment, or recirculated for other uses. For example, U.S. Pat. No. 4,424,070 (Robinson), U.S. Pat. No. 4,436,536 (Robinson), U.S. Pat. No. 4,443,237 (Ulvestad), U.S. Pat. No. 4,445,915 (Robinson), U.S. Pat. No. 5,207,812 (Tronto et al.), U.S. Pat. No. 4,954,255 (Muller et al.), U.S. Pat. No. 5,222,488 (Forsgren), and U.S. Pat. No. 5,211,846 (Kott et al.) are prior art examples of prior art cylindrical filter elements of the pleated cartridge type.
Non-cylindrical filter elements are sometimes used to process dust particles from an airstream and provide increased filtration area within a housing than cylindrical filter elements. For example, U.S. Pat. No. 5,730,766 (Clements) discloses a non-round unitary filter cartridge having a unitary structure with pleated filter media formed securely about a perforated interior core in a dust collector. U.S. Pat. No. 4,661,131 (Howeth) discloses non-cylindrical filters having a greater clean air flow area than a plurality of cylindrical elements fitted within the same dimensional envelope.
In one conventional design of air filter assembly with non-cylindrical filter elements, non-cylindrical filter elements simply replaces cylindrical filter elements. With less space between adjacent filter elements, more non-cylindrical filter elements are placed within a housing than cylindrical filter elements. U.S. Pat. No. 5,730,766 (Clements) discloses this type of use of non-cylindrical filter elements.
In another conventional design of air filter assembly with non-cylindrical filter elements, a plurality of cylindrical elements are replaced by a single non-cylindrical filter element. U.S. Pat. No. 4,661,131 (Howeth) discloses this type of use of non-cylindrical filter elements.
Unfortunately, each of these conventional designs which utilize non-cylindrical filter elements has its disadvantages and drawbacks.